Naphthyridine derivatives, their preparation and their use as phosphodiesterase isoenzyme 4 (PDE4) inhibitors

ABSTRACT

The invention relates to compounds of formula I 
                         
in free or salt form, where R 1  is a monovalent aromatic group having up to 10 carbon atoms, and R 2  is a cycloaliphatic group having up to 8 ring carbon atoms. Compositions containing them, methods for their preparation and their use as pharmaceuticals are also described.

This invention relates to organic compounds, their preparation and theiruse as pharmaceuticals.

In one aspect, the present invention provides compounds of formula I

in free or salt form, where

-   R¹ is a monovalent aromatic group having up to 10 carbon atoms, and-   R² is a cycloaliphatic group having up to 8 ring carbon atoms.

“C₁-C₈-alkyl” as used herein denotes straight chain or branchedC₁-C₈-alkyl, which may be, for example, methyl, ethyl, n-propyl,isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, straight orbranched pentyl, straight or branched hexyl, straight or branchedheptyl, or straight or branched octyl. Preferably, C₁-C₈-alkyl isC₁-C₄-alkyl.

“C₁-C₈-alkoxy” as used herein denotes straight chain or branchedC₁-C₈-alkoxy which may be, for example, methoxy, ethoxy, n-propoxy,isopropoxy, n-butoxy, isobutoxy, sec-butoxy, tert-butoxy, straight orbranched pentoxy, straight or branched hexyloxy, straight or branchedheptyloxy, or straight or branched octyloxy. Preferably, C₁-C₈-alkoxy isC₁-C₄-alkoxy.

“C₁-C₈-alkylthio” as used herein denotes straight chain or branchedC₁-C₈-alkylthio, which may be, for example, methylthio, ethylthio,n-propylthio, isopropylthio, n-butylthio, isobutylthio, sec-butylthio,tert-butylthio, straight or branched pentylthio, straight or branchedhexylthio, straight or branched heptylthio, or straight or branchedoctylthio. Preferably, C₁-C₈-alkylthio is C₁-C₄-alkylthio.

“C₁-C₈-haloalkyl” as used herein denotes C₁-C₈-alkyl as hereinbeforedefined substituted by one or more halogen atoms, preferably one, two orthree halogen atoms.

“C₁-C₈-haloalkoxy” as used herein denotes C₁-C₈-alkoxy as hereinbeforedefined substituted by one or more halogen atoms, preferably one, two orthree halogen atoms.

“C₃-C₈-cycloalkyl” as used herein denotes cycloalkyl having 3 to 8 ringcarbon atoms, for example a monocyclic group such as a cyclopropyl,cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl or cyclooctyl, any ofwhich can be substituted by one or more, usually one or two, C₁-C₄-alkylgroups, or a bicyclic group such as bicycloheptyl or bicyclooctyl.Preferably “C₃-C₈-cycloalkyl” is cyclopropyl, cyclobutyl, cyclopentyl,cyclohexyl, cycloheptyl or cyclooctyl.

“Acyl” as used herein denotes alkylcarbonyl, for exampleC₁-C₈-alkylcarbonyl where C₁-C₈-alkyl may be one of the C₁-C₈-alkylgroups hereinbefore mentioned, optionally substituted by one or morehalogen atoms; cycloalkylcarbonyl, for example C₃-C₈-cycloalkylcarbonylwhere C₃-C₈-cycloalkyl may be, for example, cyclopropyl, cyclobutyl,cyclopentyl, cyclohexyl, cycloheptyl or cyclooctyl; 5- or 6-memberedheterocyclylcarbonyl having one or two hetero atoms selected fromnitrogen, oxygen and sulfur in the ring, such as furylcarbonyl,tetrahydrofurylcarbonyl, pyrrolidinylcarbonyl, piperidinylcarbonyl orpyridylcarbonyl; arylcarbonyl, for example C₆-C₁₀-arylcarbonyl such asbenzoyl; or aralkylcarbonyl, for example C₆ toC₁₀-aryl-C₁-C₄-alkylcarbonyl such as benzylcarbonyl orphenylethylcarbonyl.

“C₁-C₈-alkoxycarbonyl” as used herein denotes C₁-C₈-alkoxy ashereinbefore defined linked through an oxygen atom thereof to a carbonylgroup.

“C₁-C₈-haloalkoxycarbonyl” as used herein denotes C₁-C₈-haloalkoxy ashereinbefore defined linked through an oxygen atom thereof to a carbonylgroup.

“C₁-C₈-hydroxyalkoxycarbonyl” and “C₁-C₈-alkoxy-C₁-C₈-alkoxycarbonyl” asused here denote C₁-C₈-alkoxycarbonyl as hereinbefore defined in whichthe C₁-C₈-alkoxy group is substituted by hydroxy or a furtherC₁-C₈-alkoxy group respectively.

“Carboxy-C₁-C₈-alkoxy” as used herein denotes C₁-C₈-alkoxy ashereinbefore defined substituted by carboxy.

“Halogen” or “halo” as used herein may be fluorine, chlorine, bromine oriodine; preferably it is fluorine, chlorine or bromine.

R¹ may be, for example, phenyl optionally substituted by one or moreelectron-withdrawing substituents, preferably selected from cyano,halogen, carboxy, aminocarbonyl, C₁-C₈-haloalkyl or C₁-C₈-haloalkoxy,preferably one or two such substituents, and/or optionally substitutedby C₁-C₈-alkyl, hydroxy, C₁-C₈-alkoxy or C₁-C₈-alkylthio, or R¹ may be aheterocyclic aromatic group having up to 10 ring atoms and 1 to 4 ringhetero atoms, preferably selected from nitrogen, oxygen and sulfur, forexample a heterocyclyl group such as furyl, thienyl, pyrrolyl,imidazolyl, pyrazolyl, furazanyl, triazolyl, tetrazolyl, oxazolyl,isoxazolyl, thiazolyl, pyridyl, pyrimidyl, pyridazinyl, triazinyl,indolyl, isoindolyl or benzimidazolyl, which heterocyclyl group may beunsubstituted or substituted e.g. by at least one C₁-C₈-alkyl, halogenor C₁-C₈-alkoxy. Preferred groups R¹ include (a) phenyl substituted bycyano, halogen (particularly fluorine or chlorine), carboxy orC₁-C₄-haloalkoxy, and optionally by C₁-C₄-alkyl or C₁-C₄-alkoxy, (b)phenyl substituted by C₁-C₄-alkoxy and (c) an aromatic heterocyclicgroup having 5 or 6 ring atoms and one or two ring hetero atoms.

R² may be, for example, a C₃-C₈-cycloalkyl group such as cyclopropyl,methylcyclopropyl, cyclobutyl, cyclopentyl, methylcyclopentyl,cyclohexyl, methylcyclohexyl, dimethylcyclohexyl, cycloheptyl,bicycloheptyl or cyclooctyl, optionally substituted by at least onesubstituent selected from C₁-C₈-alkyl, C₁-C₈-alkoxy, carboxy,C₁-C₈-alkoxycarbonyl, C₁-C₈-haloalkoxycarbonyl,C₁-C₈-hydroxyalkoxycarbonyl, C₁-C₈-alkoxy-C₁-C₈-alkoxycarbonyl,aminocarbonyl, C₁-C₈-alkylarminocarbonyl, di(C₁-C₈-alkyl)aminocarbonyl,hydroxy, acyl or C₁-C₈-alkyl optionally substituted by hydroxy, cyano,carboxy or C₁-C₈-alkoxycarbonyl. Preferably, R² is C₅-C₇-cycloalkylsubstituted by C₁-C₄-alkyl, carboxy, C₁-C₈-alkoxy-carbonyl oraminocarbonyl.

Preferred compounds of formula I in free or salt form include thosewhere

-   R¹ is phenyl substituted by one or two substituents selected from    cyano, halogen, carboxy or aminocarbonyl, and optionally by    C₁-C₈-alkoxy, or R¹ is phenyl substituted by C₁-C₄-alkoxy, hydroxy    or C₁-C₄-alkylthio, and-   R² is C₃-C₈-cycloalkyl optionally substituted by at least one    substituent selected from C₁-C₄-alkyl, carboxy, C₁-C₈-alkoxycarbonyl    or aminocarbonyl.

Further preferred compounds of formula I in free or salt form includethose where

-   R¹ is phenyl substituted by one of two substituents selected from    cyano, halogen, carboxy or aminocarbonyl meta to the indicated    naphthyridine ring and optionally by C₁-C₄-alkoxy ortho to the    indicated naphthyridine ring, or R¹ is phenyl substituted by    C₁-C₄-alkoxy meta to the indicated naphthyridine ring, and-   R² is C₅-C₇-cycloalkyl optionally substituted by at least one    substituent selected from carboxy and C₁-C₄-alkoxycarbonyl.

Other preferred compounds of formula I in free or salt form includethose where

-   R¹ is phenyl optionally substituted by one, two or three    substituents selected from the group consisting of halo, cyano,    C₁-C₈-alkyl, C₁-C₈-alkylthio, —SO—C₁-C₈-alkyl, C₁-C₈-alkoxy and    C₁-C₈-haloalkoxy, or phenyl fused with a heterocyclic ring having 3    to 8 ring atoms of which up to 4 can be carbon atoms and up to 4 can    be hetero atoms; and-   R² is C₅-C₈-cycloalkyl optionally substituted by at least one    substituent selected from the group consisting of carboxy and    carboxy-C₁-C₈-alkoxy,

Further preferred compounds of formula I in free or salt form includethose where

-   R¹ is phenyl optionally substituted by one, two or three    substituents selected from the group consisting of halo, cyano,    C₁-C₄-alkyl, C₁-C₄-alkylthio, —SO—C₁-C₄-alkyl, C₁-C₄-alkoxy and    C₁-C₄-haloalkoxy, or phenyl fused with a heterocyclic ring having 5    or 6 ring atoms of which up to 4 can be carbon atoms and up to 2 can    be hetero atoms; and-   R² is C₅-C₇ cycloalkyl optionally substituted by at least one    substituent selected from the group consisting of carboxy and    carboxy-C₁-C₄-alkoxy.

The compounds represented by formula I are capable of forming acidaddition salts, particularly pharmaceutically acceptable acid additionsalts. Pharmaceutically acceptable acid addition salts of the compoundsof formula I include those of inorganic acids, for example, hydrohalicacids such as hydrofluoric acid, hydrochloric acid, hydrobromic acid orhydroiodic acid, nitric acid, sulfuric acid, phosphoric acid; andorganic acids, for example aliphatic monocarboxylic acids such as formicacid, acetic acid, trifluoroacetic acid, propionic acid and butyricacid, aliphatic hydroxy acids such as lactic acid, citric acid, tartaricacid or malic acid, dicarboxylic acids such as maleic acid or succinicacid, aromatic carboxylic acids such as benzoic acid, p-chlorobenzoicacid, diphenylacetic acid or triphenylacetic acid, aromatic hydroxyacids such as o-hydroxybenzoic acid, p-hydroxybenzoic acid,1-hydroxynaphthalene-2-carboxylic acid or3-hydroxynaphthalene-2-carboxylic acid, and sulfonic acids such asmethanesulfonic acid or benzenesulfonic acid.

These salts may be prepared from compounds of formula I by knownsalt-forming procedures.

Compounds of formula I which contain acidic, e.g. carboxyl, groups, arealso capable of forming salts with bases, in particular pharmaceuticallyacceptable bases such as those well known in the art; suitable suchsalts include metal salts, particularly alkali metal or alkaline earthmetal salts such as sodium, potassium, magnesium or calcium salts, orsalts with ammonia or pharmaceutically acceptable organic amines orheterocyclic bases such as ethanolamines, benzylamines or pyridine.These salts may be prepared from compounds of formula I by knownsalt-forming procedures.

The compounds of formula I in free or salt form may exist instereoisomeric forms according to the orientation of moieties attachedto the cycloaliphatic ring. The invention embraces both individual suchstereoisomers, i.e. cis and trans isomers, as well as mixtures thereof.Where R¹ or R² contain an asymmetric carbon atom, the compounds offormula I in free or salt form exist in individual optically activeisomeric forms or as mixtures thereof, e.g. as racemic or diastereomericmixtures. The invention embraces both individual optically active R andS isomers as well as mixtures, e.g. racemic or diastereomeric mixtures,thereof.

Specific especially preferred compounds of formula I are those describedhereinafter in the Examples.

The present invention also provides a process for the preparation ofcompounds of formula I in free or salt form which comprises

-   (i) (A) reacting a compound of formula II

-   -   optionally in protected form, where R¹ is as hereinbefore        defined and L is a leaving atom or group, for example halogen or        an aliphatic or aromatic sulfonyloxy group such as        trifluoromethylsulfonyloxy, with a compound of formula III        X—R²  III    -   optionally in protected form, where R² is as hereinbefore        defined and X is a leaving atom or group which is reactive with        L in formula II to form a direct bond between R² and the        indicated naphthyridine ring, followed by deprotection if        required;    -   (B) reacting a compound of formula I, where R² is cycloalkyl        substituted by a C₁-C₈-alkoxycarbonyl group, to convert the        alkoxycarbonyl group into a carboxy group;    -   (C) for the preparation of compounds of formula I where R² is a        cycloaliphatic group substituted by carboxy-C₁-C₈-alkoxy,        hydrolysing a compound of formula I where R² is a cycloaliphatic        group substituted by C₁-C₈-alkoxycarbonyl-C₁-C₈-alkoxy; or    -   (D) for the preparation of compounds of formula I when R¹ is        phenyl substituted by —SO—C₁-C₈-alkyl, oxidising a compound of        formula I where R¹ is phenyl substituted by C₁-C₈-alkylthio; and

-   (ii) recovering the product in free or salt form.

Where L in formula II is an aromatic sulfonyloxy group, X may be, forexample, a group YM- where Y is halogen such as iodine and M is a metalsuch as zinc or magnesium.

Process variant (A) may be effected using known procedures for reactionof leaving atoms or groups or analogously, for example as hereinafterdescribed in the Examples. Where X in formula III is YM-, the compoundYMR² may be formed in situ by reaction of the metal M and the halideYR²; where M is zinc, this in situ reaction is conveniently effected inthe presence of dibromoethane and a trialkylsilyl halide, preferably ina solvent, e.g. an ether such as tetrahydrofuran (THF), convenientreaction temperatures being from 25 to 50° C. Reaction of the compoundof formula II with YMR² may be effected in the presence of a transitionmetal catalyst, particularly a palladium-ketone complex catalyst,1,1′-bis(diphenyl-phosphino)ferrocene and a quaternary ammonium halidesuch as tetrabutylammonium iodide, conveniently in a solvent, e.g. amixture of an ether such as THF and N-methyl-pyrrolidone(NMP),convenient reaction temperatures being from 25 to 50° C. Where it isdesired to minimise the possibility of reaction of functional groupsother than those participating in the desired reaction, such functionalgroups may be protected by conventional protecting groups.

Process variant (B) may be effected using known procedures forconversion of alkoxycarbonyl groups to carboxy groups, e.g. hydrolysiswith an aqueous alkali metal hydroxide, or analogously such ashereinafter described in the Examples.

Process variant (C) may be effected using art known procedures for thehydrolysis of esters to carboxylic acids, e.g. using trifluoroaceticacid, or analogously such as hereinafter described in the Examples.

Process variant (D) may be effected using art known procedures for theoxidation of sulfanyl groups to sulfinyl groups, e.g. using ozone orhydrogen peroxide, or analogously such as hereinafter described in theExamples.

Compounds of formula II may be prepared as described in WO98/18796 oranalogously, for example as hereinafter described in the Examples.Compounds of formula III may be prepared by known procedures, forexample in situ as described hereinbefore and (in the Examples)hereinafter.

Where reference is made herein to protected functional groups or toprotecting groups, the protecting groups may be chosen in accordancewith the nature of the functional group, for example as described inProtective Groups in Organic Synthesis, T. W. Greene and P. G. M. Wuts,John Wiley &c Sons Inc, Second Edition, 1991, which reference alsodescribes procedures suitable for replacement of the protecting groupsby hydrogen.

Compounds of formula I in free form may be converted into salt form, andvice versa, in a conventional manner. The compounds in free or salt formcan be obtained in the form of hydrates or solvates containing a solventused for crystallization. Compounds of formula I can be recovered fromreaction mixtures and purified in a conventional manner. Isomers, suchas enantiomers, may be obtained in a conventional manner, e.g. byfractional crystallization or asymmetric synthesis from correspondinglyasymmetrically substituted, e.g. optically active, starting materials.

Compounds of formula I in free or salt form are useful aspharmaceuticals. Accordingly the invention also provides a compound offormula I in free or salt form for use as a pharmaceutical. Thecompounds of formula I in free or salt form, hereinafter referred toalternatively as “AGENTS OF THE INVENTION”, exhibit cyclic nucleotidephosphodiesterase (PDE) isoenzyme inhibiting activity, selective fortype 4 isoenzyme. AGENTS OF THE INVENTION possess anti-inflammatory,anti-airways hyperreactivity and bronchodilator properties. They furtherpossess immunosuppressive and TNFα secretion inhibitory activities. Thepharmacological activities may be demonstrated in test methods, forexample as follows:

PDE4 Isoenzyme Inhibition Assay

Cloning: GATEWAY flanked PDE4 cDNA constructs containing the codingregions of the three isoenzymes, human PDE4A, human PDE4B, and humanPDE4D are generated by PCR and transposed into the GATEWAY shuttlevector pDONOR-201. In addition a 6-histidine tag is introduced by PCRonto the carboxyl terminal end of each of the constructs to facilitateprotein purification. Following sequence verification, the PDE4constructs are transposed into the GATEWAY expression vector pDEST-8,Positive recombinants are selected and transposed into E. coli strainDH10Bac and bacmid produced transfected into SF21 cells using Bac-To-Bac(Invitrogen Life Technologies). Positive transfections are selected andused to generate high titer viral stocks for use in protein expression.

PDE4 Expression: Sf21 cells are grown to a density of 2×106 cells/ml andinfected with human PDE4A, PDE4B or PDE4D3 containing baculovirus to amultiplicity of infection (m.o.i.) of 1 for 72 hours. The infected cellsare harvested by centrifugation at 1,400 g for 4 minutes at 4° C. andthe cell pellets are frozen at −80° C. Sf21 (Spodoptera frugiperda 21)insect cells are routinely maintained at densities between 3×105 and3×106 cells/ml in SF00 Serum Free Medium (Invitorgen Life Technologies).Sf21 cells (1×109) are resuspended in 100 ml cold (4° C.) Lysis Buffer(50 mM Na₂HPO4, 200 mM NaCl, 10 mM Imidazole). Cells are incubated onice for 30 minutes then centrifuged at 15,000 g for 20 minutes at 4° C.

PDE4 Purification: The 6 Histidine-tagged PDE4 proteins are isolatedfrom crude cell lysates by a batch-wise Ni-NTA purification strategy(QIAGEN). N-NTA resin is first pre-rinsed to remove ethanol preservativeand equilibrated with Lysis Buffer. Cell lysate is added, (10 ml 50%Ni-NTA slurry resin per 50 ml lysate), and gently rotated on a mixer at4° C. for 1-2 hours. The sample is then centrifuged at 1,000 g for 5minutes at 4° C. using Denley benchtop centrifuge. The supernatant isremoved and the resin is washed 3 times with 50 ml ice cold Wash Buffer(50 mM Na₂HPO4, 300 mM NaCl and 20 mM imidazole) followed bycentrifugation at 1,000 g for 5 min at 4° C. The 6His-tagged protein iseluted from the resin with 3×5 ml ice cold Elution Buffer (50 mMNaH₂PO4, 300 mM NaCl, 250 mM imidazole) and collected by centrifugationat 1,000 g for 5 minutes at 4° C. The supernatants are then pooledbefore buffer exchange and concentration using a VivaScience 20 ml SK0.2 μM Concentrator. Samples are aliquoted and stored at −20° C.

SDS-PAGE Electrophoresis: Purified PDE4 samples are analysed by SDS-PAGEusing 8-16% gradient mini-gels (Novex) and samples are denatured at 100°C. in reducing sample buffer (62 mM Tris-HCl pH 6.8, 10% glycerol, 3%SDS, 5%

-mercaptoethanol, 0.02% bromophenol blue) for 3 min prior to loading.Novex SeeBlue pre-stained MW standards are also loaded. Gels are run ata constant 25 mA. Gels are stained with GelCode Colloidal CoomassieG-250 Blue Stain Reagent (Pierce) according to the manufacturer'sprocedure.

Western Blot Analysis: Samples are analysed on Novex 8-16% gradient gelsas described above. The gel is then wet blotted onto MilliporeImmobilon-P PVDF membrane using the tank transfer method with 25 mMTris-HCl pH 8.8, 192 mM Glycine, 15% methanol transfer buffer at 80 mAfor 16 h. Immunoprobing is carried out in TTBS buffer (20 mM Tris-HCl pH7.6, 0.9% (w/v) NaCl, 0.05% (v/v) Triton X-100, 0.5% (w/v) casein) withan anti-6his monoclonal antibody (QIAGEN) at 1:1000 dilution, Ananti-mouse IgG alkaline phosphatase conjugate is used as the secondaryantibody (Sigma A9919) at 1:10000 dilution and proteins visualised withBCIP/NBT substrate prepared from tablets (Sigma) according to themanufacturers procedure,

PDE4 Assay: The assay is based on Amersham Pharmacia BiotechScintillation Proximity Assay (SPA) technology. Enzyme is diluted withenzyme dilution buffer (10 mM Tris-HCl, pH7.5 containing 1 mM EDTA) inorder to obtain between 10-30% total substrate hydrolysis during theassay. The enzymatic reaction is started by adding 10 μl diluted enzymeto 80 μl substrate (0.1 μCi [3H]-cAMP, 1 μM cAMP) and 10 μl inhibitorsolution in a 96-well microtiter plate. After 30-60 minutes incubationat room temperature the reaction is stopped by adding 50 μl PDE SPAbeads (20 mg/ml). After 30 minutes the plate is centrifuged (3000 g, 10minutes) and counted (Packard TopCount).

Inhibitor stock solutions are prepared in 100% dimethylsulphoxide (DMSO)and diluted with DMSO/water to achieve 10 concentrations to cover therange of 0-100% inhibition. The concentration of DMSO is kept constantat 1% (v/v) throughout the assay.

The concentration at which 50% inhibition occurs (IC₅₀) is determinedfrom inhibition—concentration curves in a conventional manner. Withinthe PDE4 isoenzyme group, AGENTS OF THE INVENTION generally exhibitselectivity for inhibition of PDE4D isoenzyme relative to PDE4A, PDE4Band PDE4C. The compounds of Examples 1, 3, 10, 12, 14 and 15 have IC₅₀values of 38, 9, 25, 21, 57 and 9 nM respectively for inhibition ofPDE4D in the above assay.

Having regard to their inhibition of binding of PDE4, AGENTS OF THEINVENTION are useful in the treatment of conditions mediated by PDE4,particularly inflammatory conditions. Treatment in accordance with theinvention may be symptomatic or prophylactic.

Accordingly, AGENTS OF THE INVENTION are useful in the treatment ofinflammatory or obstructive airways diseases, resulting, for example, inreduction of tissue damage, bronchial hyperreactivity, remodeling ordisease progression. Inflammatory or obstructive airways diseases towhich the present invention is applicable include asthma of whatevertype or genesis including both intrinsic (non-allergic) asthma andextrinsic (allergic) asthma, mild asthma, moderate asthma, severeasthma, bronchitic asthma, exercise-induced asthma, occupational asthmaand asthma induced following bacterial or viral infection. Treatment ofasthma is also to be understood as embracing treatment of subjects, e.g.of less than 4 or 5 years of age, exhibiting wheezing symptoms anddiagnosed or diagnosable as “wheezy infants”, an established patientcategory of major medical concern and now often identified as incipientor early-phase asthmatics. (For convenience this particular asthmaticcondition is referred to as “wheezy-infant syndrome”.)

Prophylactic efficacy in the treatment of asthma will be evidenced byreduced frequency or severity of symptomatic attack, e.g. of acuteasthmatic or bronchoconstrictor attack, improvement in lung function orimproved airways hyperreactivity. It may further be evidenced by reducedrequirement for other, symptomatic therapy, i.e. therapy for or intendedto restrict or abort symptomatic attack when it occurs, for exampleanti-inflammatory (e.g. corticosteroid) or bronchodilatory. Prophylacticbenefit in asthma may in particular be apparent in subjects prone to“morning dipping”. “Morning dipping” is a recognised asthmatic syndrome,common to a substantial percentage of asthmatics and characterised byasthma attack, e.g. between the hours of about 4 to 6 am, i.e. at a timenormally substantially distant form any previously administeredsymptomatic asthma therapy.

Other inflammatory or obstructive airways diseases and conditions towhich the present invention is applicable include acute lung injury(ALI), adult/acute respiratory distress syndrome (ARDS), chronicobstructive pulmonary, airways or lung disease (COPD, COAD or COLD),including chronic bronchitis or dyspnea associated therewith, emphysema,as well as exacerbation of airways hyperreactivity consequent to otherdrug therapy, in particular other inhaled drug therapy. The invention isalso applicable to the treatment of bronchitis of whatever type orgenesis including, e.g., acute, arachidic, catarrhal, croupus, chronicor phthinoid bronchitis. Further inflammatory or obstructive airwaysdiseases to which the present invention is applicable includepneumoconiosis (an inflammatory, commonly occupational, disease of thelungs, frequently accompanied by airways obstruction, whether chronic oracute, and occasioned by repeated inhalation of dusts) of whatever typeor genesis, including, for example, aluminosis, anthracosis, asbestosis,chalicosis, ptilosis, siderosis, silicosis, tabacosis and byssinosis,

Having regard to their anti-inflammatory activity, their influence onairways hyperreactivity and their profile in relation to PDE isoenzymeinhibition, in particular as selective type 4 inhibitors, AGENTS OF THEINVENTION are useful for the treatment, in particular prophylactictreatment, of obstructive or inflammatory airways disease. Thus bycontinued and regular administration over prolonged periods of timeAGENTS OF THE INVENTION are useful in providing advance protectionagainst recurrence of bronchoconstrictor or other symptomatic attackconsequential to obstructive or inflammatory airways disease or for thecontrol, amelioration or reversal of basal status of such disease.

Having regard to their bronchodilator activity AGENTS OF THE INVENTIONare useful as bronchodilators, e.g. for the treatment of chronic oracute broncho-constriction, e.g. for the symptomatic treatment ofobstructive or inflammatory airways disease.

Having regard to their activity as selective inhibitors of TNF-αrelease, AGENTS OF THE INVENTION are also useful for the down-regulationor inhibition of TNF-α release, e.g. for the treatment of diseases orconditions in which TNF-α release is implicated or plays a mediatingrole, e.g. diseases or conditions having an aetiology involving orcomprising morbid, for example undesirable, excessive or unregulatedTNF-α release, in particular for the treatment of cachexia or endotoxinshock and in treatment of AIDS [cf. Sharief et al, Mediators ofInflammation, 1 323-338 (1992)], the treatment of cachexia associatedwith morbid TNF-α release or TNF-α blood-serum levels of whateverorigin, including cachexia consequential to, e.g. bacterial, viral orparasitic, infection or to deprivation or deterioration of humoral orother organic, e.g. renal function, the treatment of cancerous, malarialand vermal cachexia, cachexia resulting from dysfunction of thepituitary, thyroid or thymus glands as well as uremic cachexia and, inparticular, the treatment of AIDS-related cachexia, i.e. cachexiaconsequential to or associated with to HIV infection.

The method of the invention is also applicable to the treatment ofseptic shock, e.g., shock conditions resulting from bacterial infection.In this regard it is to be noted that the present invention provides amethod for the treatment of septic shock as such as well as ofconditions consequential to or symptomatic of septic or shock, forexample ARDS.

The AGENTS OF THE INVENTION are further applicable to the treatment ofdisease consequential to HIV infection, e.g. AIDS, e.g. to theamelioration or control of the advance of such disease.

Having regard to their profile in relation to inhibition of PDEisoenzymes and/or TNF-α release inhibition, as well as theirimmunosuppressive activity, AGENTS OF THE INVENTION are also useful asimmunosuppressive agents, e.g. for the treatment of autoimmune diseases,in particular for the treatment of autoimmune diseases in whichinflammatory processes are implicated or which have an inflammatorycomponent or aetiology, or as anti-inflammatory agents for the treatmentof inflammatory disease in particular for the treatment of inflammatorydisease in which autoimmune reactions are implicated or which have anautoimmune component or aetiology. Examples of such disease to which thepresent invention is applicable include autoimmune hematologicaldisorders (e.g. hemolytic anaemia, aplastic anaemia, pure red cellanaemia and idiopathic thrombocytopenia), systemic lupus erythematosus,polychondritis, scleroderma, Wegener granulomatosis, dermatomyositis,chronic active hepatitis, myasthenia gravis, Steven-Johnson syndrome,idiopathic sprue, autoimmune inflammatory bowel disease (e.g. ulcerativecolitis and Crohn's disease), endocrine ophthalmopathy, Grave's disease,sarcoidosis, alveolitis, chronic hypersensitivity pneumonitis, multiplesclerosis, primary biliary cirrhosis, juvenile diabetes (diabetesmellitus type I), uveitis (anterior and posterior), keratoconjunctivitissicca and vernal keratoconjunctivitis, interstitial lung fibrosis,psoriatic arthritis and glomerulonephritis (with and without nephroticsyndrome, e.g. including idiopathic nephrotic syndrome or minimal changenephropathy), as well as inflammatory and/or hyperproliferative skindiseases such as psoriasis, atopic dermatitis, pemphigus and, inparticular, contact dermatitis, e.g. allergic contact dermatitis.

AGENTS OF THE INVENTION are in particular useful for the treatment ofarthritis, and other rheumatic or inflammatory disease, especially forthe treatment of rheumatoid arthritis.

As immunosuppressants AGENTS OF THE INVENTION are further useful in theprevention of graft rejection, e.g. for the maintenance of allogenicorgan transplants or the like, e.g. in relation to kidney, liver, lung,heart, heart-lung, bowel, bone-marrow, skin, or corneal transplant.

Having regard to their profile in relation to inhibition of PDEisoenzymes, in particular their profile as selective type 4 inhibitors,AGENTS OF THE INVENTION are further useful for the treatment of diseaseinvolving tissue calcium depletion, in particular degenerative diseasesof the bone and joint involving calcium depletion, especiallyosteoporosis. In this regard they are further useful for the treatmentof allergic inflammatory diseases such as rhinitis, conjunctivitis,atopic dermatitis, urticaria and gastrointestinal allergies; asvasodilators, e.g. for the treatment of angina, hypertension,ischaemia/reperfusion injury, congestive heart failure and multi-infarctdementia; and for the treatment of other conditions where inhibition ofPDE 4 is indicated, for example, depression, conditions and diseasescharacterised by impaired cognitive function including Alzheimer'sdisease, Parkinson's disease and stroke.

The AGENTS OF THE INVENTION are also useful as co-therapeutic agents incombination with other drug substances such as anti-inflammatory,bronchodilatory, antihistamine or immunosuppressive drug substances,particularly in the treatment of inflammatory diseases e.g. obstructiveor inflammatory airways diseases, autoimmune diseases or graft rejectionsuch as those mentioned hereinbefore, for example as potentiators oftherapeutic activity of such drugs or as a means of reducing requireddosaging or potential side effects of such drugs. An agent of theinvention may be mixed with the other drug substance in a fixedpharmaceutical composition or it may be administered separately, before,simultaneously with or after the other drug substance. Suchanti-inflammatory drugs include steroids, in particularglucocorticosteroids such as budesonide, beclamethasone, fluticasone,ciclesonide or mometasone, LTB4 antagonists such as those described inU.S. Pat. No. 5,451,700 and LTD4 antagonists such as montelukast andzafirlukast, dopamine receptor agonists such as cabergoline,bromocriptine, ropinirole and4-hydroxy-7-[2-[[2-[[3-(2-phenylethoxy)propyl]-sulfonyl]ethyl]-amino]ethyl]-2(3H)-benzothiazoloneand pharmaceutically acceptable salts thereof (the hydrochloride beingViozan®-AstraZeneca). Such bronchodilatory drugs include anticholinergicor antimuscarinic agents, in particular ipratropium bromide, oxitropiumbromide and tiotropiurm bromide, and beta-2 adrenoceptor agonists suchas salbutamol, terbutaline, salmeterol and, especially, formoterol andpharmaceutically acceptable salts thereof, and compounds (in free orsalt or solvate form) of formula I of PCT International Publication No.WO 00/175114, which document is incorporated herein by reference,preferably compounds of the Examples thereof, especially a compound offormula

and pharmaceutically acceptable salts thereof. Co-therapeuticantihistamine drug substances include cetirizine hydrochloride,acetaminophen, clemastine fumarate, promethazine, loratidine,desloratidine, diphenhydramine and fexofenadine hydrochloride.Co-therapeutic immunosuppressive drug substances include, e.g.cyclopeptide, cyclopeptolide or macrolide drug substances, for examplesdrugs belonging to the cyclosporin class, e.g. cyclosporins A or G, thedrug substances tacrolimus (also known as FK 506), ascomycin andrapamycin and their various known congeners and derivatives.

Combinations of AGENTS OF THE INVENTION and steroids, beta-2 agonists,or LTD4 antagonists may be used, for example, in the treatment of COPDor, particularly, asthma. Combinations of AGENTS OF THE INVENTION andanticholinergic or antimuscarinic agents, PDE4 inhibitors, dopaminereceptor agonists or LTB4 antagonists may be used, for example, in thetreatment of asthma or, particularly, COPD. Combinations of AGENTS OFTHE INVENTION and immunosuppressive drug substances may be used in thetreatment of any disease or condition requiring immunosuppressivetreatment as hereinbefore described.

Other useful co-therapeutic combinations of AGENTS OF THE INVENTIONinclude combinations with PDE3 inhibitors such as those disclosed in WO00/166123, e.g. revizinone, ci-lostamide, amipizone, siguazodan,carbazeran, bemoradan, motapizone and, particularly, milrinone,enoximone and pimopendan, especially for treatment of conditionscharacterised by acute or chronic obstruction of vessels and/or bronchiand/or acute or chronic inflammation, e.g. acute obstructive bronchitis,bronchial asthma or COPD.

In accordance with the foregoing, the present invention also provides amethod for the treatment of a disease mediated by PDE4 which comprisesadministering to a subject, particularly a human subject, in needthereof an effective amount a compound of formula I, or apharmaceutically acceptable salt thereof, as hereinbefore described. Inanother aspect, the invention provides a compound of formula I, or apharmaceutically acceptable salt thereof, as hereinbefore described foruse in the preparation of a medicament for the treatment of a diseasemediated by PDE4.

In accordance with the foregoing, the present invention also provides amethod for the treatment of an inflammatory disease, particularly anobstructive or inflammatory airways disease, which comprisesadministering to a subject, particularly a human subject, in needthereof an effective amount a compound of formula I, or apharmaceutically acceptable salt thereof, as hereinbefore described. Inanother aspect, the invention provides a compound of formula I, or apharmaceutically acceptable salt thereof, as hereinbefore described foruse in the preparation of a medicament for the treatment of aninflammatory disease, particularly an obstructive or inflammatoryairways disease.

The AGENTS OF THE INVENTION may be administered by any appropriateroute, e.g. orally, for example in the form of a tablet or capsule;parenterally, for example intravenously; topically to the skin, forexample in the treatment of psoriasis; intranasally, for example in thetreatment of rhinitis; or by inhalation, particularly in the treatmentof obstructive or inflammatory airways diseases.

In a further aspect, the invention also provides a pharmaceuticalcomposition comprising as active ingredient a compound of formula I infree form or in the form of a pharmaceutically acceptable salt thereof,optionally together with a pharmaceutically acceptable diluent orcarrier therefor. Such compositions may be prepared using conventionaldiluents or excipients and techniques known in the galenic art. Thusoral dosage forms may include tablets, capsules and controlled releaseformulations such as encapsulated or matrix dissolution formulations,osmotic system formulations or ion exchange resin formulations.Formulations for topical administration may take the form of creams,ointments, gels or transdermal delivery systems, e.g. patches.Compositions for inhalation may comprise aerosol or other atomizableformulations or dry powder formulations.

When the composition comprises an aerosol formulation, it preferablycontains, for example, a hydro-fluoro-alkane (HFA) propellant such asHFA134a or HFA227 or a mixture of these, and may contain one or moreco-solvents known in the art such as ethanol (up to 20% by weight),and/or one or more surfactants such as oleic acid or sorbitan trioleate,and/or one or more bulking agents such as lactose.

When the composition comprises a dry powder formulation, it preferablycontains, for example, a compound of formula I having a particlediameter up to 10 microns, optionally together with a diluent orcarrier, such as lactose, of the desired particle size distribution anda compound that helps to protect against product performancedeterioration due to moisture.

When the composition comprises a nebulised formulation, it preferablycontains, for example, a compound of formula I either dissolved, orsuspended, in a vehicle containing water, a co-solvent such as ethanolor propylene glycol and a stabiliser, which may be a surfactant.

The invention also includes (A) a compound of formula I as hereinbeforedescribed in free form, or a pharmaceutically acceptable salt or solvatethereof, in inhalable form; (B) an inhalable medicament comprising sucha compound in inhalable form together with a pharmaceutically acceptablecarrier in inhalable form; (C) a pharmaceutical product comprising sucha compound in inhalable form in association with an inhalation device;and (D) an inhalation device containing such a compound in inhalableform.

Dosages employed in practising the invention will of course varydepending, for example, on the particular condition to be treated, theeffect desired and the mode of administration. In general, suitabledaily dosages for oral administration are of the order of 0.5 to 200 mg,while suitable daily dosages for administration by inhalation are of theorder of from 0.1 to 10 mg.

The invention is illustrated by the following Examples.6-Amino-8-bromo-1,7-naphthyridine used in the Examples is prepared asdescribed in WO98/18796.

EXAMPLE 14[8-(3-Cyano-phenyl)-[1,7]naphthyridin-6-yl]-cyclohexanecarboxylic acidethyl ester 6-amino-8-(3-cyanophenyl)-1,7-naphthyridine

To a mixture of tetrahydrofuran (THF) (80 ml) and 2 N sodium carbonate(34 ml, aqueous) is added 6-amino-8-bromo-1,7-naphthyridine (4.007 g),triphenylphosphine (0.37 g) and 3-cyanophenylboronic acid (323 g). Themixture is degassed under argon three times and thenbis(dibenzylideneacetone)palladium (0) (0.4 g) is added and the mixtureis degassed under argon three more times. The mixture is heated at 80°C. under argon for 16 hours then cooled and filtered. The mixture isdiluted with ethyl acetate and washed with 2 N sodium hydroxide thenbrine. After drying over sodium sulfate the organic layer is evaporatedand suspended in ether. The solid precipitate thus obtained is the titlecompound, which is filtered off. M.p. 182-184° C. HRMS [M+H]⁺found=247.1.

6-Trifluromethanesulfonyl-8-(3 cyanophenyl)-1,7-naphthyridine—Compound A

To a solution of 6-amino-8-(3-cyanophenyl)-1,7-naphthyridine (4.058 g)in dimethylform-amide (DMF) (22 ml) under argon at 0° C. is addedtrifluoromethanesulfonic acid (11 ml). The mixture is stirred at 0° C.for 10 minutes and then sodium nitrite (2.26 g) is added slowly. Thecooling bath is then removed and the mixture stirred at room temperaturefor 3 hours. The resulting mixture is diluted with ethyl acetate andwashed with water, 2 M NaOH and water again. The organic layer is driedover sodium sulfate, then concentrated in vacuo and purified by columnchromatography, eluting with 10:0.5 toluene:acetone to yield the titlecompound. M.p. 102-104° C. MS (m/e)=380.1

4-Iodo-cyclohexanecarboxylic acid ethyl ester—Compound B

To a cold (0° C.) stirred solution of 4-hydroxy-cyclohexanecarboxylicacid ethyl ester (1.0 g, 5.80 mmol) in 1:2 CH₂Cl₂/CCl₄ (52 ml) is addedtriphenylphosphine (1.82 g, 6.96 mmol), imidazole (473 mg, 6.96 mmol),and iodine (1.79 g, 7.08 mmol). The reaction is allowed to warm to roomtemperature and stirred overnight. The reaction is quenched by theaddition of saturated sodium thiosulphate (c.a. 50 ml) and stirred untilthe solution becomes clear. The layers are separated and the aqueouslayer is extracted with CH₂Cl₂ (3×30 ml). The combined organic phasesare washed with sodium thiosulphate (30 ml), brine (30 ml), dried withanhydrous MgSO₄, filtered and evaporated at reduced pressure to an oilysolid. Purification by dry flash chromatography, Keiselgel 15-40 gradesilica, eluting with 3% ethyl acetate/iso hexane yields the titlecompound as a clear colourless oil.

4-[8-(3-Cyano-phenyl)-[1,7]naphthyridin-6-yl]-cyclohexanecarboxylic acidethyl ester

A flask is charged with activated zinc dust (742 mg, 11.13 mmol), THF(1.80 ml) and 1,2-dibromoethane (25 μl 0.284 mmol). The suspension isheated to reflux for 3 minutes and then allowed to cool beforetrimethylsilyl chloride (29 μl, 0.227 mmol) is added. The mixture isstirred for 15 minutes, then Compound B (1.60 g, 5.67 mmol) is added andthe mixture stirred at 35° C. for 1.5 hours. A second flask is chargedwith Pd (dibenzylideneacetone)₂ (101 mg, 0.176 mmol),1,1′-bis(diphenyl-phosphino)ferrocene (98 mg, 0.176 mmol),N-methylpyrrolidinone (NMP) (3 ml):THF (1 ml), tetrabutylammonium iodide(2.79 g, 7.56 mmol) and Compound A (956 mg, 2.52 mmol and the contentsare added to the first flask at 35° C. The reaction is stirred for 2hours, then quenched by the addition of water (15 ml) and stirred forten minutes. Ethyl acetate (40 ml) is then added and stirred for 5minutes. The layers are separated and the organic layer is washed with5% citric acid (25 ml), water (2×25 ml), and brine (40 ml), dried withanhydrous MgSO₄, filtered and evaporated to brown viscous oil.Purification is by dry flash chromatography using 15-40 grade Keiselgelsilica, eluting with 30% ethyl acetate/iso-hexane to yield the titlecompound as an orange gum. MH⁺ 386.0.

EXAMPLE 24-[8-(3-Cyano-phenyl)-[1,7]naphthyridin-6-yl]-cyclohexanecarboxylic acid

A solution of lithium hydroxide (6.5 mg, 0.155 mmol) in water (160 μl)is added to a solution of4-[8-(3-cyano-phenyl)-[1,7]naphthyridin-6-yl]-cyclohexane carboxylicacid ethyl ester (60 mg, 0.155 mmol) in NMP(0.16 ml). Upon completion,the reaction is diluted with water and washed with ethyl acetate (5 ml).The aqueous layer is acidified with 5% citric acid and the product isextracted into ethyl acetate. The organic layer is dried over brine (10ml) and anhydrous MgSO₄, filtered and evaporated. Purification by flashchromatography using Keiselgel 40-63 grade silica and eluting with 1.5%CH₃OH:0.5% CH₃COOH: dichloromethane affords the title compound. MH⁺357.0. mp 179.8-180.3° C.

EXAMPLE 34-[8-(3-Cyano-phenyl)-[1,7]naphthyridin-6-yl]-cyclohexanecarboxylic acid

Potassium Salt

4-[8-(3-Cyano-phenyl)-[1,7]naphthyridin-6-yl]-cyclohexanecarboxylic acid(24 mg, 0.067 m mol)) is dissolved in methanol (c.a. 2 ml) and anhydrousK₂CO₃ (4.6 mg, 0.035 mmol) is added. The suspension is ultra-sonicatedfor 15 minutes or until the K₂CO₃ is dissolved. Evaporation of themethanol and subsequent trituration of the resulting salt with bothethyl acetate and diethyl ether followed by drying gives the titlecompound. MH⁺ 357.0 (parent acid). Mp>250° C.

EXAMPLE 44-[8-(3-Carbamoyl-pheny4)-[1,7]naphthyridin-6-yl]-cyclohexanecarboxylicacid

Sodium hydroxide (4 M, 0.5 ml) is added to a solution of4-[8-(3-cyano-phenyl)-[1,7]naphthyridin 6-yl]-cyclohexanecarboxylic acidethyl ester (65 mg, 0.168 mmol) in NMP/CH₃OH/H₂O (0.50 ml, 8:1:1) andthe solution is left stirring overnight. The solution is acidified withaqueous 5% citric acid and extracted into ethyl acetate (3×10 ml). Theorganic layer is dried over brine, anhydrous MgSO₄, filtered andevaporated at reduced pressure to a yellow gum. Purification is by massspectrometry guided preparative HPLC (column: Xterra ms c8 5 μm 19×50mm) to give the title compound. MH⁺ APCI 376.0.

EXAMPLE 5 3-[6-(4-Carboxy-cyclohexyl)-[1,7]naphthyridin-8-yl]-benzoicacid

This is prepared analogously to Example 4, purification by massspectrometry guided preparative HPLC (column: Xterra c8 5 μm 19×50 mm)affording the title compound. MH⁺ APCI 377.1

EXAMPLE 64-[8-(5-Fluoro-2-methoxy-phenyl)-[1,7]naphthyridin-6-yl]-cyclohexanecarboxylicacid ethyl ester

This is prepared analogously to Example 1, from trifluoromethanesulfonicacid 8-(5-fluoro-2-methoxy-phenyl)-[1,7]-naphthyridin-6-yl ester as thestarting material. MH+ APCI 409.0.

EXAMPLE 74-[8-(5-Fluoro-2-methoxy-phenyl)-[1,7]naphthyridin-6-yl]-cyclohexanecarboxylicacid

This is prepared, analogously to Example 2, from the product of Example6, the product being purified by mass spectrometry guided HPLC (column:Xterra ms c8 5 μm 19×50 mm) to give the title compound as a yellow gum.MH⁺ 381.1.

EXAMPLE 84-[8-(5-Fluoro-2-methoxy-phenyl)-[1,7]naphthyridin-6-yl]-cyclohexanecarboxylicacid sodium salt

This is prepared, analogously to Example 3, from the product of Example7, using anhydrous Na₂CO₃. MH⁺ 381.1 (parent acid seen).

EXAMPLES 9-19

By procedures analogous to the appropriate Examples above, and usingappropriate starting materials, compounds of formula I are obtained asidentified in Table I together with mass spectrometry characterisingdata (MS:APCI MH⁺). The compounds are obtained in free form, except forExample 11 that is isolated as the potassium salt.

TABLE I Ex. No R¹ R² MS 9

368.6 10

362.9 11

388.184 12

350.6 13

367.0 14

417.65 15

379.05 16

395.87 17

347.06 18

386.8 19

407.16 20

377.12 21

381.16 22

333.71

EXAMPLE 104-[8-(3-Methoxy-phenyl)-[1,7]naphthyridin-6-yl]-cyclohexanecarboxylicacid

Potassium hydroxide (2 M, 0.9 ml) is added to a solution of4-[8-(3-Methoxy-phenyl)-[1,7]naphthyridin-6-yl]-cyclohexanecarboxylicacid ethyl ester (230 mg, 0.6 mmol) in THF/ethanol (6 ml:2 ml) andheated at 80° C. for 3 hours. The solution is then diluted with ethylacetate (120 ml) and extracted with water. The aqueous layer is taken topH 4 with 1M HCl to give a white precipitate, which is extracted intodichloromethane (DCM). The DCM layer is washed with water, then driedover magnesium sulfate, filtered and concentrated to yield the desiredproduct. M.p 209-212° C. MS (AP⁺) 362.9

4-[8-(3-Methoxy-phenyl)-[1,7]naphthyridin-6-yl]-cyclohexanecarboxylicacid ethyl ester

This compound is prepared in an analogous way to compound4-[8-(3-Cyano-phenyl)-[1,7]naphthyridin-6-yl]-cyclohexanecarboxylic acidethyl ester from trifluoromethanesulfonic acid8-(3-methoxy-phenyl)-[1,7]naphthyridin-6-yl ester. Purification is bychromatography followed by trituration with ether to yield a whitesolid. MS (AP⁺) 391.0

Trifluoromethanesulfonic acid8-(3-methoxy-phenyl)-[1.7]naphthyridin-6-yl ester

This compound is prepared in an analogous way to Compound A. MS (TOFES+) 384.97

EXAMPLE 11 Potassium {4-[8-(3-cyano-phenyl)[1,7]naphthyridin-6-yl]-cyclohexyloxy}-acetate

Potassium carbonate (10.1 mg, 0.074 mmol) in water (1 ml) is added to asolution of{4-[8-(3-cyano-phenyl)-[1,7]naphthyridin-6-yl]cyclohexyloxy}-acetic acid(59 mg, 0.15 mmol) in methanol (6 ml). The reaction mixture is stirredat room temperature for 30 minutes, filtered and concentrated. Theproduct is lyophilised from water (×3) then dried at 40° C. in vacuo for18 hours. Recrystallisation from CH₂Cl₂/ether gives the product. m.p148-150° C. (decomp.) MS (ES⁺) [M+H]⁺ 388.1635

{4-[8-(3-cyano-phenyl)-[1.7]naphthyridin-6-yl]-cyclohexyloxy}-aceticacid

Trifluoroacetic acid (TFA) (2 ml) is added to a solution of{4-[8-(3-cyano-phenyl)-[1,7]naphthyridin-6-yl]-cyclohexyloxy}-aceticacid tert-butyl ester (182 mg, 0.41 mmol) in CH₂Cl₂ (2 ml) at 0° C. Thesolution is stirred at room temperature for 1 hour, concentrated, andazeotroped with toluene (×3). Purification by chromatography on silicagel, eluting with 7% methanol in CH₂Cl₂ gives the product. MS (ES⁺)[M+H]⁺ 388.04

{4-[8-(3-cyano-phenyl)-[1.7]naphthyridin-6-yl]-cyclohexyloxy}-aceticacid tert-butyl ester

1,2-Dibromoethane (12 μl) is added to a slurry of zinc dust (589 mg, 9.0mmol) in tetrahydrofuran (THF) (0.9 ml), The mixture is heated at refluxfor 3 minutes then allowed to cool to room temperature.trimethylsilylchloride (TMSCl) (15 μl) is added and the mixture isstirred at room temperature for 30 minutes.(4-iodo-cyclohexyloxy)-acetic acid tert-butyl ester (cis:trans=ca. 1:1)(680 mg, 2.0 mmol) in THF (1 ml) is added via syringe and the mixture isheated at 40° C. for 2 hours. A solution of Bu₄NI i.e.tetrabutylammonium iodide (1.1 g, 3.0 mmol), Pd(dba)₂ i.e. palladiumdibenzylideneacetone (40 mg, 0.07 mmol), dppf i.e.1,1′-bis(diphenylphosphino)ferrocene (39 mg, 0.07 mmol) and Compound A(372 mg, 1.0 mmol) in THF (2 ml)/NMP(2 ml) is added and the mixture isheated at 40° C. for 18 hours then allowed to cool to room temperature.The reaction mixture is diluted with ethyl acetate and filtered overCelite. The filtrate is washed with sat. aq. NH₄Cl (×1), 10% aq. citricacid (×1), water (×1) and brine (×1), dried (MgSO₄), filtered andconcentrated. Purification by chromatography on silica gel, eluting with30% ethyl acetate in isohexane gives the trans product. MS (ES⁺) [M+H]⁺444.10

(4-iodo-cyclohexyloxy)-acetic acid tert-butyl ester

Triphenylphosphine (1.18 g, 4.49 mmol), imidazole (0.31 g, 4.49 mmol)and iodine (1.14 g, 4.49 mmol) are added to a solution of(4-hydroxy-cyclohexyloxy)-acetic acid tert-butyl ester (cis:trans=ca.1:1) (0.86 g, 3.74 mmol) in a mixture of CH₂Cl₂ (10 ml)/CCl₄ (20 ml) at0° C. The cooling bath is removed and the reaction mixture is stirred atroom temperature for 18 hours. Saturated aq. Na₂S₂O₃ (10 ml) is addedand the mixture is stirred for 15 minutes. The layers are separated andthe aqueous layer is re-extracted with CH₂Cl₂ (×3). The combined organicextracts are washed with brine (×1), dried (Na₂SO₄), filtered andconcentrated. Purification by chromatography on silica gel, eluting with5% ethyl acetate in isohexane, gives the product.

EXAMPLE 124-[8-(3-Fluorophenyl)-[1,7]naphthyridin-6-yl]-cyclohexanecarboxylic acid

Lithium hydroxide (1M (aq), 24.3 ml, 24.3 mmol) is added to a solutionof 4-[8-(3-fluorophenyl)-[1,7]naphthyridin-6-yl]-cyclohexanecarboxylicacid ethyl ester (4.60 g, 12.14 mmol) in THF/methanol (40 ml:20 ml) andstirred at room temperature overnight. The organic solvents are removedby evaporation, then the aqueous residue diluted with water and basifiedto pH9 with 1M KOH. The aqueous layer is then washed with ethyl acetate(3×). The aqueous layer is acidified to pH 4 with 1M HCl to give a whiteprecipitate, which is extracted into ethyl acetate. The ethyl acetatelayer is then dried over sodium sulfate, filtered and concentrated toyield the desired product as a yellow foam. Further trituration with 1MHCl yields the product as a pale yellow powder (2.153 g). MS (AP⁺) 350.6

4-[8-(3-Fluorophenyl)-[1,7]naphthyridin-6-yl]-cyclohexanecarboxylic acidethyl ester

This compound is prepared in an analogous way to compound4-[8-(3-cyano-phenyl)-[1,7]naphthyridin-6-yl]-cyclohexanecarboxylic acidethyl ester from trifluoromethanesulfonic acid8-(3-flurophenyl)-[1,7]naphthyridin-6-yl ester. Purification is bychromatography followed by trituration with ether to yield a whitesolid. MS (AP⁺) 378.98

Trifluoromethanesulfonic acid 8-(3-fluorophenyl)-[1,7]naphthyridin-6-ylester

This compound is prepared in an analogous way to Compound A. MS (TOFES+) 372.87

EXAMPLE 144-[8-(3-Trifluoromethoxyphenyl)-[1,7]naphthyridin-6-yl]-cyclohexanecarboxylicacid

Potassium hydroxide (2M (aq), 2.5 ml) is added to a solution of4-[8-(3-trifluoromethoxyphenyl)-[1,7]naphthyridin-6-yl]-cyclohexanecarboxylicacid ethyl ester (250 mg, 0.56 mmol) in ethanol (10 ml) and stirred 45°C. for 1 h. The reaction mixture is diluted with water and acidifiedwith c.HCl to pH3. The mixture is stirred for 2 h. then filtered, andthe filter cake washed with water to yield the product as a white powder(218 mg). MS (AP⁺) 417.65

4-[8-(3-Trifluoromethoxyphenyl)-[1,7]naphthyridin-6-yl]-cyclohexanecarboxylicacid ethyl ester

This compound is prepared in an analogous way to compound4-[8-(3-cyano-phenyl)-[1,7]naphthyridin-6-yl]-cyclohexanecarboxylic acidethyl ester from trifluoromethanesulfonic acid8-(3-trifluromethoxyphenyl)-[1,7]naphthyridin-6-yl ester. Purificationis by chromatography followed by trituration with ether to yield a whitesolid. MS (AP⁺) 445

Trifluoromethanesulfonic acid 8-(3-fluorophenyl)-[1,7]naphthyridin-6-ylester

This compound is prepared in an analogous way to Compound A. MS (TOFES+) 438.3

EXAMPLE 154-[8-(3-Methylsulfanyl-phenyl)-[1,7]naphthyridin-6-yl]-cyclohexanecarboxylicacid

Lithium hydroxide (168 mg, 1.76 mmol) in water (1.7 ml) is added to asolution of4-[8-(3-methylsulfanyl-phenyl)-[1,7]naphthyridin-6-yl]-cyclohexanecarboxylicacid ethyl ester (650 mg, 1.6 mmol) in THF (3.2 ml) under argon.Methanol is added to maintain solution (4 ml) and the mixture is stirredat room temperature for 5 hours. The mixture is evaporated to drynessthen partitioned between ethyl acetate and water. The aqueous layer isacidified to pH 2 then extracted into ethylacetate and dried overmagnesium sulfate, Evaporation gives a green gum which is reevaporatedfrom methanol then DCM/diethylether to give a yellow/green foam. Thefoam is triturated with 3:1 hexane:diethyl ether, 2:1hexane:diethylether, ethylacetate/hexane/ether mixtures and finally 5:1diethylether:ethanol to yield an off-white solid. This is thenrecrystallised from ethanol to yield the title compound. M.p177.6-178.2° C., MS (AP⁺) 379.05

4-[8-(3-Methylsulfanyl-phenyl)-[1,7]-naphthyridin-6-yl]-cyclohexanecarboxylicacid ethyl ester

This compound is prepared in an analogous way to4-[8-(3-cyano-phenyl)-[1,7]naphthyridin-6-yl]-cyclohexanecarboxylic acidethyl ester from the analogous starting materials. MS (AP⁺) 407.2

EXAMPLE 164-[8-(3-Methanesulfinyl-phenyl)-[1,7]naphthyridin-6-yl]-cyclohexanecarboxylicacid

A solution of4-[8-(3-Methanesulfanyl-phenyl)-[1,7]naphthyridin-6-yl]-cyclohexanecarboxylicacid (30 mg, 0.079 mmol) in THF (1.4 ml) is cooled in a salt/ice bathand oxone (14.5 mg, 0.024 mmol) in water (0.5 ml) is added. After 15minutes the reaction mixture is allowed to warm to room temperature andafter a further 30 minutes more oxone (14.5 mg is added). The mixture isdiluted with ethyl acetate/water and the aqueous layer extracted withethyl acetate. The combined organic layers are washed with brine thendried over magnesium sulfate. Filtration followed by evaporation yieldsa foam consisting of title compound and4-[8-(3-Methanesulfonyl-phenyl)-[1,7]naphthyridin-6-yl]-cyclohexanecarboxylicacid. MS (AP⁺) 395.87

EXAMPLES 9, 13, 17, 18 and 22

Compounds of these Examples are made by an analogous procedure toExample 10 and may be isolated as either the free acid or as a salt, forexample the potassium salt.

EXAMPLES 19, 20 and 21

Compounds of these Examples are made by an analogous procedure toExample 11 and may be isolated as either the free acid or as a salt, forexample the potassium salt.

1. A compound of formula I

in free or salt form, where R ¹is a monovalent aromatic group having upto 10 carbon atoms, and R² is C₃-C₈-cycloalkyl optionally substituted byat least one substituent selected from C₁-C₄-alkyl, carboxy,C₁-C₈-alkoxycarbonyl or aminocarbonyl.
 2. A compound according to claim1, in which R¹ is phenyl substituted by one or two substituents selectedfrom cyano, halogen, carboxy or aminocarbonyl, and optionally byC₁-C₈-alkoxy, or R¹ is phenyl substituted by C₁-C₄-alkoxy, hydroxy orC₁-C₄-alkylthio.
 3. A compound according to claim 1, in which R¹ isphenyl substituted by one or two substituents selected from cyano,halogen, carboxy or aminocarbonyl meta to the indicated naphthyridinering and optionally by C₁-C₄-alkoxy ortho to the indicated naphthyridinering, or R¹ is phenyl substituted by C₁-C₄-alkoxy meta to the indicatednaphthyridine ring, and R² is C₅-C₇-cycloalkyl optionally substituted byat least one substituent selected from carboxy and C₁-C₄-alkoxycarbonyl.4. A compound according to claim 1 in which R¹ is phenyl optionallysubstituted by one, two or three substituents selected from the groupconsisting of halo, cyano, C₁-C₈-alkyl, C₁-C₈-alkylthio,—SO—C₁-C₈-alkyl, C₁-C₈-alkoxy and C₁-C₈-haloalkoxy; and R² isC₃-C₈-cycloalkyl optionally substituted by at least one substituentselected from the group consisting of carboxy and carboxy-C₁-C₈-alkoxy.5. A compound according to claim 1, in which R¹ is phenyl optionallysubstituted by one, two or three substituents selected from the groupconsisting of halo, cyano, C₁-C₄-alkyl, C₁-C₄-alkylthio,—SO—C₁-C₄-alkyl, C₁-C₄-alkoxy and C₁-C₄-haloalkoxy; and R² isC₅-C₇-cycloalkyl optionally substituted by at least one substituentselected from the group consisting of carboxy and carboxy-C₁-C₄-alkoxy.6. A compound according to claim 1, which is 4-[8-(3-cyano-phenyl)-[1,7]naphthyridin-6-yl]-cyclohexanecarboxylic acid ethyl ester,4-[8-(3-cyano-phenyl) -[1,7]naphthyridin-6-yl]-cyclohexanecarboxylicacid, 4-[8-(3-cyano-phenyl)-[1,7]naphthyridin-6-yl]-cyclohexane-carboxylic acid potassium salt,4-[8-(3-carbamoyl-phenyl)-[1,7]naphthyridin-6-yl]-cyclo-hexanecarboxylicacid, 3-[6-(4-carboxy-cyclohexyl)-[1,7]naphthyridin-8-yl]-benzoic acid,4-[8-(5-fluoro-2-methoxy-phenyl)-[1,7]naphthyridin-6-yl]-cyclohexanecarboxylicacid ethyl ester, 4-[8-(5-fluoro-2-methoxy-phenyl)-[1,7]naphthyridin-6-yl]-cyclohexanecarboxylic acid, or4-[8-(5-fluoro-2-methoxy-phenyl)-[1,7]naphthyridin-6-yl]-cyclohexanecarboxylic acid sodium salt.
 7. Acompound according to claim 1, in which R¹ and R² are as listed in thefollowing table: R¹ R²


8. A process for the preparation of compounds of formula I in free orsalt form which comprises (i) (A) reacting a compound of formula II

optionally in protected form, where R¹ is as defined in claim 1 and L isa leaving atom or group, with a compound of formula IIIX-R²  III optionally in protected form, where R² is as defined in claim1 and X is a leaving atom or group which is reactive with L in formulaIto form a direct bond between R² and the indicated naphthyridine ring,followed by deprotection if required, or (B) reacting a compound offormula I, where R² is cycloalkyl substituted by a C₁-C₈-alkoxycarbonylgroup, to convert the alkoxycarbonyl group into a carboxy group, and(ii) recovering the product in free or salt form.
 9. A pharmaceuticalcomposition comprising a compound according to claim 1, optionallytogether with a pharmaceutically acceptable diluent or carrier.
 10. Apharmaceutical composition comprising a compound according to claim 6,optionally together with a pharmaceutically acceptable diluent orcarrier.
 11. A pharmaceutical composition comprising a compoundaccording to claim 7, optionally together with a pharmaceuticallyacceptable diluent or carrier.
 12. A method of treating an obstructiveor inflammatory airways disease in a subject in need of such treatment,which comprises administering to said subject an effective amount of acompound of formula I as defined in claim 1 in free form or in the formof a pharmaceutically acceptable salt.
 13. A method of treating anobstructive or inflammatory airways disease in a subject in need of suchtreatment, which comprises administering to said subject an effectiveamount of a compound of formula I as defined in claim 6 in free form orin the form of a pharmaceutically acceptable salt.
 14. A method oftreating an obstructive or inflammatory airways disease in a subject inneed of such treatment, which comprises administering to said subject aneffective amount of a compound of formula I as defined in claim 7 infree form or in the form of a pharmaceutically acceptable salt.